leetcode13

描述

Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an em...

Lecture3

自动机

• 一个有穷自动机可以接收$\epsilon$

  无穷自动机

• $\delta$: $Q \times \Sigma_\epsilon \to P(Q)$
• 幂级
...

题目

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol Value I 1 V 5 X 10 L 5...

题目

Seven different symbols represent Roman numerals with the following values:

Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 Roman numerals are formed by appending ...